To: Joe Parisi, Dane County Executive
RE: Addressing the risk of flooding in the Yahara Lakes
The Yahara Lakes Association (YLA) appreciates your efforts and leadership to improve the quality of our lakes. The extensive flooding in our community this summer and the potential for even more extreme weather events make it clear that we now need your leadership to address the real risk of catastrophic flooding in the Yahara Chain of Lakes.
The catastrophic impact of the recent flooding on both public and private property owners in Dane County has been estimated to be more than $154 million. The modeling of the Yahara Lakes flood risk has used parameters from the June 2008 storm that led to the Lake Delton Dam break (the what-if the Lake Delton storm had happened in Madison scenario). Now we have “what-if the August 2018 storm that inundated Middleton/Black Earth and Cross Plains had been located five miles to the east”. We don’t need to settle the question of whether these storms were made more intense by global warming or that there will be an increasing number of storms in the future. We just need to understand that in the last ten years, two storms, within an hour of Madison, have dropped over 12 inches of rain in 24 hours. The recent flooding on the lakes was from 4-5 inches of rain on August 20th and followed by several weeks of on and off rain.
Just imagine the damage from one 12 inch rain event.
This is a risk we can no longer ignore and we must take steps now to mitigate the impact. So once again, we need your leadership to address the real risk of catastrophic flooding on the Yahara Chain of Lakes.
As a first step, we request that you include three items in your 2019 Budget.
Funding for additional weed harvesting machines and operating funds. We are investing in the Yahara River, especially between Lake Waubesa and Kegonsa and also between Kegonsa and the Stoughton Dam insures maximum water flow out of the Yahara River.
Funding to identify and remove obstructions in the Yahara River. This summer, water flow out of Lake Kegonsa was effectively stopped by sediment build up under the railroad bridge below Lake Kegonsa. If this happened in one spot, it is likely happening in other locations. The county staff must proactively identify obstructions in the Yahara River that need to be removed and also where dredging is needed.
Funding for a technical group of experts to develop options to mitigate the risk of catastrophic flooding from extreme weather events. Although a stakeholders group along the lines of the previous YLAG groups may be necessary, we understand you also plan to organize a small group of experts to work with County staff to develop and model options to mitigate the impact of an extreme weather event. We support this concept and believe it is the most effective way to make quick progress to avoid future floods.
We believe the group should deliver recommendations by early Spring 2019 and consider the following broad questions:
a. What can be one to enhance the flow of water out of the Yahara lakes?
b. What can be done to reduce the flow of water into the system during the extreme weather events?
c. What can be done to increase the storage capacity of the Yahara Lakes?
d. What can be done to better protect the public and private property exposed to this flood risk?
Also, below are questions for the Technical Group to consider:
What can be done to enhance the flow of water out of the Yahara Lakes? a) What should be the targets for water flow out of Lake Waubesa and out of Lake Kegonsa that will quickly identify water flow issues in the Yahara river? b) Are the plans to remove obstructions from the Yahara river sufficient to insure maximum flow of the river? c) Are there opportunities to create alternative areas to divert the water for permanent or temporary storage? d) Can the design or operation of any or all of the dams in the system be modified to enhance the rate of flow out of the lakes in high water conditions?
What can be done to reduce the flow of water into the system during extreme weather events? a) Can changes in runoff rules and regulations governing wetlands materially change the flow into the lakes during extreme weather events? b) Are there opportunities to divert the flow of water into the lakes for temporary storage?
What can be done to Increase the storage capacity of the Yahara lakes? a) Can the Tenney Park Locks be fortified to allow Lake Mendota to safely reach water levels higher than current maximum of around 852.2? b) Should the target maximum levels be reduced in any or all of the lakes? What are the impacts of such a reduction? Should the target minimum levels also be reduced? c) What is the process to modify the lake level targets? d) What changes can be made to the current operating protocols to enhance the ability to stay within lake level targets? Should rules be removed on when to start moving to winter minimum or return to summer minimum? e) Do we need to consider projects (i.e. dredging lake channels) to offset the impact of lowered lake level targets?
What can be done to better protect the public and private property exposed to this risk? a) Can shorelines be raised or protective berms be built? Can we determine an appropriate level for shorelines or berm projects for each lake and provide guidelines to the public? b) Can and should we close off storm sewers that serve as passage ways to deliver water to neighborhoods not even located on the lake and river shorelines? c) Should utility lines be relocated so power can continue to be delivered to sandbagged property to support continued pumping and prevent property losses? Do we have an adequate supply of generators?
This is certainly not an exhaustive list and we are confident the group will come up with many other questions and potential solutions.
Thank you so much for your leadership on the many issues facing our lakes! We look forward to working with you on addressing this challenge. We would welcome the opportunity to meet with you to further discuss this issue. You can contact Dan Schultz, the YLA President via our YLA office to arrange a meeting.
Regards, Yahara Lakes Association Board of Directors